Education Secretary Betsy DeVos has been the most aggressive of cabinet secretaries in following an executive order issued by President Trump that required cabinet heads to shrink the federal footprint.CreditCreditTom Brenner/The New York Times

WASHINGTON — Federal labor mediators have advised the Education Department that it most likely imposed new work rules on its employees illegally, curtailing workers’ protections and access to union representation in violation of federal law.

The American Federation of Government Employees said Tuesday that the Federal Labor Relations Authority advised the Education Department that it had engaged in “bad-faith bargaining” when it implemented a contract this year that gutted compensation and benefits provisions for the department’s 3,900 employees, and limited employees’ ability to carry out union duties during the work day.

The decision could have broad implications because the Education Department’s actions mirror Trump administration efforts throughout the federal government. The Social Security Administration and the Department of Veterans Affairs have begun implementing work rules similar to the ones at the Education Department, union officials said. And many of the anti-union elements reflect a series of executive orders on the federal work force that President Trump signed in May.

The union plans to use the finding as it pursues labor disputes across the federal government.

“For the first salvo to be knocked down by the F.L.R.A., it sends the message that the government isn’t going to be allowed to operate outside the bounds of the law,” said David A. Borer, general counsel for the union.

The Education Department imposed the contract after a year of contentious, intermittent talks with the union fell apart in February. Each side accused the other of refusing to show up at the bargaining table. In March, the department announced a “collective bargaining agreement” that officials said reflected its final offer.

The union contends that it had not negotiated any provisions, and therefore had agreed to nothing, making the department’s imposition of its offer an “illegal edict.” It filed an unfair labor practices charge with the labor relations authority in March.

Nathan Bailey, a spokesman for the Education Department, said the contract was imposed because “the union spent more than a year, dating back into the Obama administration, dragging its feet on ground rules for negotiations without reaching any agreement, and then failed to respond in a timely manner to negotiate over the contract proposed by the department.”

He declined to comment on the labor authority’s advisory, citing pending litigation. But a senior department official said the labor authority had repeatedly ruled that federal agencies could unilaterally implement contracts if the union had failed to respond in a timely manner in contract negotiations, as the department argues happened in this case.

The labor authority, an independent government agency that investigates and resolves government-labor disputes, currently has no general counsel and therefore cannot issue decisions that would allow the violation finding to be formally charged and litigated.

But the decision, made by a regional director after a four-month investigation, reflects an independent finding by a civil servant that the union’s case has merit.

“It’s a real spoke in the wheel in the government’s attempt to destroy federal sector unions,” Mr. Borer said. “This was the first salvo in what’s become a broadening assault on federal unions, the rights of federal workers.”

A spokeswoman for the labor authority declined to comment because the agency does not comment on pending litigation.

The union, which represents more than 700,000 federal government employees across 70 federal agencies, said the Education Department’s contract put into force the president’s vision for the federal work force. His executive orders, which were preceded by a series of anti-union statements in the president’s budget, made it easier to fire government employees by overhauling evaluation and grievance processes, ordered agencies to renegotiate their union contracts to cut down on “waste,” and pared back “official time” that government workers could use to represent employees.

The union will receive its first court hearing on the matter on Wednesday, and Mr. Borer said he was hopeful that the advisory would bolster his case.

Trump officials said the orders would help improve performance at historically dysfunctional agencies, like the Department of Veterans Affairs, and would rein in abuses of official time that allowed some employees to spend all their time on union activities. Administration officials said the measures would save the government at least $100 million a year.

It also evicted union representatives from the department’s offices and barred them from using government equipment. The new rules also require union representatives to get permission from their bosses to carry out their union duties. And they limit disputes that are subject to grievance procedures, while vastly expanding the kinds of disputes that are not. The work rules also eliminate an anti-retaliation guarantee.

When the work rules were implemented, Liz Hill, a department spokeswoman, said they complied with all federal labor laws and that the goal was “to treat all employees and the American taxpayers fairly.”

But union officials accused the department of “union busting.” They noted that Education Secretary Betsy DeVos has long been a critic of labor unions — she has publicly traded barbs with the leaders of teachers’ unions — and said the department has taken unprecedented measures to weaken the union’s power and presence.

The work rules were imposed during a tumultuous spring for department employees, as Ms. DeVos has sought to shrink and reorganize the agency. Ms. DeVos has been the most aggressive of the cabinet secretaries in following an executive order issued by Mr. Trump at the beginning of his administration that required cabinet heads to shrink the federal footprint.

Ms. DeVos has cut staff by offering buyouts, has scattered expertise by reassigning a number of high-profile managers and has tried to break up the department’s budget office. Some parts of the plan have drawn protests from the White House’s Office of Management and Budget, and Congress has sought to halt parts of the reorganization through legislation. However, Ms. DeVos has won some praise for streamlining the department, including reducing the number of political appointees.

In a May testimony before the House Education Committee, Ms. DeVos said her reorganization plan, which also included consolidating offices and streamlining the agency’s functions, was created “to more efficiently serve students and the taxpayer.”

“These reforms are not rooted in a partisan ideology, nor are they designed to benefit one group over another,” she said. “They are focused solely on the students, parents and teachers I meet each week — and millions more like them.”

But union officials said the reorganization and the union contract was emblematic of the Trump administration’s larger goal.

“What’s going on at the Department of Education is what we can expect to see governmentwide from this president and his political appointees as they move to dismantle the government work force that supports our democracy,” said J. David Cox Sr., the president of the union’s national office.

A version of this article appears in print on , on Page A15 of the New York edition with the headline: Education Dept. Illegally Put Limits on Union Protections, Mediators Say. Order Reprints | Today’s Paper | Subscribe